1. Field of the Invention
The present invention concerns a method for the dimensioning of engineering drawings, which are preferably created using a CAD program.
2. Description of Related Art
Computers are increasingly used for the creation of engineering drawings. A computer typically comprises two display devices, namely a screen and a printer, a keyboard having about 100 keys, two drives for removable memory mediums, and a mouse, which can be used for moving a pointing means (cursor) on the display screen. Typically, the computer further comprises a working memory, a non-volatile mass memory, and a processor. Special peripheral devices for the creation of engineering drawings are a tablet in connection with a pen for entering commands and drawing elements like lines or circles. Often computers are connected to a network for exchanging data with other computers.
A multitude of programs is available for the computer aided creation of engineering drawings. Simple programs require that each line and each dimension figure is entered individually. Many programs permit to combine lines to form an area and to provide the area with a hatching.
A large part of the time used for creating an engineering drawing is taken up by the dimensionings. A dimensioning comprises a dimension figure, a dimension line, and one or two auxiliary lines. Consequently a total of three to four elements must be entered. Two points must be defined for entering one line. Because of this, six points must be entered by the user for entering two auxiliary lines and one dimension line for creating one dimensioning. It is time-consuming and thus not user-friendly that the two points defining the dimension line must be located on one auxiliary line each. Therefore the user has to position the pointing means very exactly before entering these two points.
Some CAD programs therefore support the user in the creation of dimensionings by not requiring him to enter each element of the dimensioning individually. Before a dimensioning is created, it is laid down as an option in the CAD program whether the dimension and auxiliary lines are to run horizontally, vertically or diagonally. For entering one dimensioning the user has to define two points, which are to be dimensioned, using a pointing means, which may, for example, be moved using a mouse. The auxiliary lines run through these points. Furthermore, the user defines a third point using the pointing means, the dimension line running through this point. The dimension figure is determined automatically by the CAD program on the basis of the distance of the two auxiliary lines, and it is entered into the drawing at the dimension line. Consequently, in order to enter a dimensioning, the user now only has to define three points, preferably by clicking thereon, for each dimensioning.
When a dimensioning is entered in a direct, computer aided way, the dimension line is defined by entering one point only. The position of this point in the direction perpendicular to the auxiliary lines does not influence the position of the dimension line. The position of this point parallel to the auxiliary lines at most has an aesthetic significance. The point, which defines the dimension line, therefore does not have to be entered exactly, but only approximately. An only approximate positioning of the pointing means by the user can be done more quickly and therefore is more user-friendly.
However, there is still the disadvantage associated with the entering of dimensionings that the two points, which define the auxiliary lines, must be positioned exactly with respect to the body edges. Some CAD programs therefore have some snap-in grid, which can be activated, or a so-called capture function. When the snap-in grid or capture function is activated, the pointing means is moved during the entering process, i.e., for example, the mouse click, onto the line already entered. Because of this, the user again has the advantage that he only needs to position the pointing means approximately.
For entering drawing elements like, for example, lines, typically more data are required than are in fact entered. Typically only the start and end points are entered for a line. Further data like, for example, the line width, color and end points are stored as options in the program before entering the line and are then available for entering a plurality of lines. Options therefore are program settings, which are valid for a plurality of inputs and can be changed either before or after inputs.
As a rule, a plurality of drawing elements like, for example, a line, a circle or a text, are displayed on the screen completely or in part. A data structure on the working memory corresponds to each of the elements displayed on the screen. Following the method of object oriented programming, data structures are also called data objects. In this application only data objects are of interest which can be displayed on the screen as graphical objects. Normally only a small number of the data objects stored on the working memory are displayed as graphical objects because of the small dimensions of the screen. Therefore the terms xe2x80x9cdata objectxe2x80x9d and xe2x80x9cgraphical objectxe2x80x9d can often be used as synonyms.
Many CAD programs allow to combine a plurality of elements of a drawing in a group. The group then behaves like an element. All elements of a group can, for example, be moved, copied or deleted jointly. Since groups behave like elements, they can be joined with further groups or elements to even more extensive groups. Groups and elements are both called objects.
More often than not, a drawing is composed of a plurality of graphical objects. One or more drawings are located on a sheet. A plurality of sheets form a folder or a project. Most CAD programs follow this division.
The object of the present invention is to provide a method by which a dimensioning can be added to data objects defining an engineering drawing in an easy way. This object is accomplished by the subject-matter of patent claim 1. The dependent claims concern preferred embodiments of the present invention.
The dimensioning object according to the invention preferably comprises a plurality of data objects like, for example, auxiliary or dimension lines. It is created automatically on the basis of dimensioning rules. The user may influence the direction of dimensioning and the distance of the dimension lines from the data objects by positioning the pointing means. Before creating the dimensioning object, the user may select data objects by dragging the mouse, whereby a preferably rectangular region is defined on the display device. All data objects are selected whose graphical representation is located completely inside the rectangular region. Furthermore the user may influence the dimensioning object by selecting different dimensioning styles.
The points to be dimensioned are preferably determined in a two-stage process. In the first stage the contours of the data objects are analyzed, and the contour points are determined. In the second stage the points to be dimensioned are determined from the contour points. The user may influence the points to be dimensioned in the first stage by selecting the data objects and, in particular, in the second stage by moving the pointing means. After the points to be dimensioned are determined, a preliminary dimensioning is generated and displayed. The preliminary dimensioning preferably only comprises part of the final dimensioning object. On the basis of a change of position of the pointing means, the points to be dimensioned and a preliminary dimensioning are determined from the contour points again and again, such that the user may influence the preliminary dimensioning interactively. If the user accepts the dimensioning, the dimensioning object is stored together with the other data objects of the drawing.